1. Field of the Invention
The present disclosure relates generally to the field of vehicle seating. More specifically, this disclosure relates to a back frame for a vehicle seat.
2. Brief Description of the Related Art
Vehicle seats generally include a lower structure joined a back frame coupled together with a recliner mechanism. A foam core and a trim cover, typically of a fabric or a leather material, are disposed around the lower and back frames for supporting a passenger in the vehicle.
FIG. 1 is a perspective view of one type of a back frame 20 for a vehicle seat. The back frame 20 includes a pair of vertical sections 22 interconnected by a horizontally extending upper section 24 and a horizontally extending lower section 26. The upper and lower sections 24, 26 extend in spaced and approximately parallel relationship with one another. Although not shown in FIG. 1, a head restraint for supporting the head of the passenger is generally attached to the top of the upper section 24 of the back frame 20.
FIG. 2 is a side view of a back frame 20 in an automobile during a rear end collision, or a rear impact. As shown, the back frame 20 is disposed in a seat in the front row of a passenger vehicle and supporting the back of a first row passenger 28. A head restraint 30 extends upwardly from the upper section 24 of the back frame 20 to support the head of the first row passenger 28. As illustrated with an arrow, the rear end collision causes the head of the first row passenger 28 to impart a longitudinally backward force (F1) on the head restraint 30, creating whiplash in the neck of the first row passenger 28. This backward force (F1) creates a moment (M1y) about an axis running through the upper section 24 of the back frame 20. The upper section 24 of the back frame 20 must withstand this moment (M1y), i.e. the upper section 28 must be torsionally rigid enough to prevent relative movement of the head of the first row passenger 28, or to prevent whiplash.
FIG. 3 is a side view of a back frame 20 in an automobile that is experiencing a front end collision, or a front impact. As shown, the back frame 20 is disposed in the front row of the automobile and supporting the back of a first row passenger 28. A head restraint 30 extends upwardly from the upper section 24 of the back frame 20. Additionally, a second passenger 32 is disposed in a back row of the automobile, seated behind the back frame 20 in the front row. As illustrated with an arrow, the head of the second passenger 32 imparts a large longitudinal forward force (F2) on the head restraint 30 of the back frame 20 in the front row. This forward force (F2) creates a moment (M2y) about an axis running through the upper section 24 of the back frame 20. The direction of the moment (M1y) from the rear end collision is opposite the direction of the moment (M2y) from the front end collision. The upper section 24 of the first row back frame 20 has to comply with certain torsional rigidity requirements that support the safety of the second row occupant during a front impact.
Various reinforcements have been developed to ensure that the upper section 24 of the back frame 20 withstands even the most violent collisions. One way to reinforce the upper section 24 of the back frame 20 is shown in the back frame 20 of FIGS. 4 and 5. FIG. 4 is a front view of the back frame 20 and FIG. 5 is a rear view of the back frame 20. In this example, a U-channel bracket 34 is disposed in a U-shaped channel 36 in the upper section 24 of the back frame 20. The U-shaped channel 36 and U-channel bracket 34 each extend horizontally between the vertical sections 22 of the back frame 20. Additionally, a pair of spaced tubes 38 extend vertically through the U-shaped channel 36 of the upper section 24 of the back frame 20 for supporting the head restraint 30. Joints (not shown) are required to connect the tubes 38 to the U-channel bracket 34 and to connect the U-channel bracket 38 to the U-shaped channel 36. Each of these parts, i.e. the U-channel bracket 34 and the joints, adds to the cost and manufacturing complexity of the back frame 20.
There remains a significant and continuing need for back frames for vehicle that are both cost effective and strong enough to withstand the moments that are applied to the back frame during front or rear impacts.